For example, a device mounted on a vehicle to generate compressed air to be used in the vehicle is known as disclosed in Japanese Utility Model Registration No. 3150077. The device disclosed in Japanese Utility Model Registration No. 3150077 includes a plurality of air compressors and a plurality of drive motors. Each air compressor is driven by each drive motor. Each air compressor is coupled in series to the corresponding drive motor. Note that each air compressor is configured as a scroll air compressor.
In the device disclosed in Japanese Utility Model Registration No. 3150077, the air compressors and the drive motors are coupled in series. Thus, a dimension of an air compressor unit including the air compressors and the drive motors becomes long. Then, an installation area required in mounting and installing this air compressor unit on a vehicle becomes long and wide.
The air compressor unit as described above is installed below a floor of the vehicle as also disclosed in Japanese Utility Model Registration No. 3150077. Thus, to install the above air compressor unit on the vehicle, a large and wide area is necessary below the floor of the vehicle. Further, even in the case of installing the above air compressor unit on a roof of the vehicle, a large and wide area is necessary on the roof of the vehicle. Accordingly, in the case of installing the above air compressor unit, it leads to an increase of the installation area on the vehicle. Further, in the case of installing a plurality of air compressor units in the vehicle, it leads to a further increase of the installation area.